Authentication answers 'who are you?' — verifying an identity, typically via credentials like a username/password or a token. Authorization answers 'what are you allowed to do?' — determining whether an already-authenticated identity has permission to perform a specific action or access a specific resource. Spring Security handles both, but as distinct, sequential concerns: authentication must succeed before authorization checks are meaningful.

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#Authentication#Authorization

What is the difference between authentication and authorization?

A 401 vs a 403 Response Maps Directly to This Distinction

HTTP 401 Unauthorized actually means 'authentication failed or is missing' (a misleading name, historically), while 403 Forbidden means 'you're authenticated, but not authorized for this specific action' — Spring Security returns these two distinct status codes precisely because it treats authentication failure and authorization failure as separate, independently detectable outcomes.

Authentication: verifying who you are · Authorization: deciding what you're allowed to do, once identity is established